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 A281662 (Denominator of Bernoulli(2*n)) read mod n. 2
 0, 0, 0, 2, 1, 0, 6, 6, 6, 0, 6, 6, 6, 2, 12, 14, 6, 12, 6, 10, 0, 8, 6, 18, 16, 4, 15, 2, 6, 0, 6, 30, 9, 30, 31, 30, 6, 30, 3, 10, 6, 0, 6, 30, 3, 30, 6, 42, 6, 30, 42, 30, 6, 30, 33, 6, 42, 30, 6, 30, 6, 30, 42, 62, 1, 24, 6, 30, 42, 50, 6, 6, 6, 30, 72, 30, 61 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Odd terms at: 5, 27, 33, 35, 39, 45, 55, 65, 77, 81, 99, 105, 121, etc. - Robert G. Wilson v, Jan 26 2017 LINKS Seiichi Manyama, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A002445(n) mod n. MATHEMATICA f[n_] := Mod[Denominator[BernoulliB[2 n]], n]; Array[f, 77] (* Robert G. Wilson v, Jan 26 2017 *) PROG (Ruby) def bernoulli(n)   ary = []   a = []   (0..n).each{|i|     a << 1r / (i + 1)     i.downto(1){|j| a[j - 1] = j * (a[j - 1] - a[j])}     ary << a[0]   }   ary end def A281662(n)   a = bernoulli(2 * n)   (1..n).map{|i| a[2 * i].denominator % i} end (PARI) a(n) = denominator(bernfrac(2*n)) % n; \\ Michel Marcus, Jan 29 2017 CROSSREFS Cf. A002445, A106741, A281648. Sequence in context: A271703 A276922 A129062 * A163936 A288874 A187555 Adjacent sequences:  A281659 A281660 A281661 * A281663 A281664 A281665 KEYWORD nonn AUTHOR Seiichi Manyama, Jan 26 2017 STATUS approved

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Last modified March 30 12:10 EDT 2020. Contains 333125 sequences. (Running on oeis4.)